Semiconductor image sensors are used for sensing light. Complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) and charge-coupled device (CCD) sensors are widely used in various applications such as digital still camera or mobile phone camera applications.
A backside illuminated (BSI) image sensor device is one type of image sensor device. Image pixels in the BSI image sensor device generate electrical signals in response to incident light. Magnitudes of the electrical signals depend on the intensity of the incident light received by the respective image pixels. However, as the size of transistor devices shrinks with each technological generation, existing BSI image sensor devices may begin to suffer from issues related to electrical or optical crosstalk. These issues may be caused by insufficient isolation between neighboring image pixels of the BSI image sensor device. Thus, a sufficient isolation structure is required.